Electronically Controlled Viscous Cooling Fan

Cooling fan clutches have been used on GM vehicles for many years, because they improve fuel economy and emissions, and contribute to lower engine noise levels. Historically, most rear-drive vehicles have been equipped with a thermostatic fan clutch, or in some cases, an electric fan. The 4.2L engine (RPO LL8) in the 2002 Chevrolet TrailBlazer, GMC Envoy, and Oldsmobile Bravada uses an all-new PCM-controlled Electro-Viscous (EV) cooling fan. In 2003, this same device will appear on the 5.3L (LM4) mid-size truck engine.
When compared with the conventional fan clutch, the EV fan offers several benefits:
– Improved A/C idle and city traffic performance
– Reduced noise
– Reduced A/C compressor warranty, because the A/C system operates at a lower head pressure

In the past, if you were working on a vehicle condition that was not addressed in SI, you could check the list of Product Information (PI) documents to see if one of the titles sounded like it would be helpful. Then you had to call Technical Assistance for specific repair suggestions contained in the PI. Changes were put in place on the SI website the week of June 17 allowing you to find both the title and the text of Product Information documents yourself. And, the CD version will be updated to reflect the PI enhancement in July when a new set of SI CDs are shipped to your dealership.

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